With continuous development of various application technologies, users are increasingly depending on services provided on an IP network: enterprise users expect that an Internet Protocol (IP) network can provide secure and reliable services such as a private line service, a voice over Internet protocol (VOIP) service, and a video conference service, so as to save operating expenses of enterprises; and individual users also expect to gain better multimedia experience from the IP network, including services such as a high-quality IP television service, a video chat service, and a real-time gaming service. In addition, with large-scale deployment of a next generation network (NGN)/third generation mobile telecommunications technologies (3rd-generation, 3G), a broadband access network is required for bearing an NGN/3G service, so as to reduce costs of the entire network solutions. All the foregoing cases require that the broadband access network has a quality of service (QoS) processing capability to bear services of different QoS requirements.
Generally, a typical broadband access network is a layer 2 network. In a downlink direction of the layer 2 network, because traffic in a high-speed line is forwarded to a low-speed line, if QoS processing is not performed, congestion may occur, and consequently, QoS of a borne service cannot be ensured. If a broadband remote access server (BRAS) is capable of predicating, according to a forwarding path of a packet and a bearing capability of all links from the BRAS to a terminal, whether congestion occurs during forwarding of the packet over the broadband access network, and taking corresponding measures, occurrence of the congestion can be avoided. A link from the BRAS to the terminal traverses devices such as the BRAS, a local area network switch (LAN Switch), a digital subscriber line access multiplexer (DSLAM), customer premise equipment (CPE), and the terminal, and a link rate gradually decreases. Therefore, there is a hierarchical QoS processing process, that is, an HQoS process.
During construction of a mobile IP backhaul network, generally, a mobile operator does not have optical fiber transmission resources, and therefore, needs to lease transmission resources of a fixed network operator to connect a base station and a base station controller. In the foregoing application scenario, the fixed network operator promises to provide a layer 2 tunnel with a certain rate for the mobile operator, while a packet exceeding the rate will be discarded. To ensure that a data packet of the mobile operator is not discarded by the fixed network operator, the mobile operator needs to perform predictable HQoS processing to ensure that a rate of a packet reaching the layer 2 tunnel of the fixed network operator is less than a committed rate of the layer 2 tunnel.
However, at present, risks are relatively concentrated during an HQoS control process.